2.2. Composition
The compositionof a gypsumboard canbe determined bymeans
of thermal analysis techniques, such as the thermogravimetric
method (TGA), or by simply heating samples at specific temperatures,
i.e. in an oven, and weighting before and after the treatment,
and then measuring the mass loss. Assuming that fm, CS, MC,
CC and O are the mass percentages of the free moisture content,
the calcium sulphates, the magnesium carbonates, the calcium carbonates
and the other materials that do not participate in any of
the reactions, of a gypsum board and knowing the mass loss percentages
of a “heated up” gypsum sample during the dehydration
and evaporation of the chemically bound water (ımdh-CS) and the
decomposition of magnesium (ımdc-MC) and calcium (ımdc-CC) carbonate,
allows the formulationofmass balance equations according
to [26], with respect to the reactions described by Eqs. (2.1)–(2.7),
which define the initial composition of the gypsum board:
CS = ımdh-CS
1 − MWCS-AH
MWCS-DH
MC = ımdc-MC
1 − MWMO
MWMC
CC = ımdc-CC
1 − MWCO
MWCC
O = 1 − fm − CS − MC − CC
(2.10)
2.3. Reaction energy
The energy that is absorbed during the evaporation of the free
moisture content can be calculated from:
Hfm = fmLv (2.11)
The energy that is absorbed during the dehydration of calcium
sulphate dihydrate is the summation of the energy needed for the
dissociation of the chemically bound water from the crystal lattice
and that needed for the evaporation of this amount of water:
Hdh-CS=CSHds-cbw + ımdh-CSLv=
Hds-cbw
1 − MWCS-AH
MWCS-DH
+ Lv
ımdh-CS
(2.12)
where Hds-cbw
2.2. CompositionThe compositionof a gypsumboard canbe determined bymeansof thermal analysis techniques, such as the thermogravimetricmethod (TGA), or by simply heating samples at specific temperatures,i.e. in an oven, and weighting before and after the treatment,and then measuring the mass loss. Assuming that fm, CS, MC,CC and O are the mass percentages of the free moisture content,the calcium sulphates, the magnesium carbonates, the calcium carbonatesand the other materials that do not participate in any ofthe reactions, of a gypsum board and knowing the mass loss percentagesof a “heated up” gypsum sample during the dehydrationand evaporation of the chemically bound water (ımdh-CS) and thedecomposition of magnesium (ımdc-MC) and calcium (ımdc-CC) carbonate,allows the formulationofmass balance equations accordingto [26], with respect to the reactions described by Eqs. (2.1)–(2.7),which define the initial composition of the gypsum board:CS = ımdh-CS1 − MWCS-AHMWCS-DHMC = ımdc-MC1 − MWMOMWMCCC = ımdc-CC1 − MWCOMWCCO = 1 − fm − CS − MC − CC(2.10)2.3. Reaction energyThe energy that is absorbed during the evaporation of the freemoisture content can be calculated from:Hfm = fmLv (2.11)The energy that is absorbed during the dehydration of calciumsulphate dihydrate is the summation of the energy needed for thedissociation of the chemically bound water from the crystal latticeand that needed for the evaporation of this amount of water:Hdh-CS=CSHds-cbw + ımdh-CSLv=Hds-cbw1 − MWCS-AHMWCS-DH+ Lvımdh-CS(2.12)where Hds-cbw
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